648 abstracts: geology 



The anticlinal folds that trend obliquely to the course of the main 

 range appear to be the chief structural features governing the accu- 

 mulation of oil. The petroleum has apparently migrated, both verti- 

 cally, from the organically formed shales into the more porous sand- 

 stones that overlie them, and laterally up the dip through the porous 

 beds. Shale lying beneath the broad San Joaquin Valley is believed 

 to have yielded much of the oil now found in the anticlines along the 

 foothills. The oblique folds appear to have a protecting influence upon 

 the concentration of petroleum in the main range, for oil occurs not 

 only along the higher parts of the oblique anticlines but also in the 

 flank of the main range just back of these folds, or in other words in 

 the flanks of the sjmcline that lies between the oblique anticline and 

 the main range. Oil is not found, however, in the flank of the range 

 where there s no anticlinal fold lying between the main range and the 

 San Joaquin Valley. R. W. P. 



GEOLOGY. — -The -phosphate deposits of Florida. G. C. Matson. 

 U. S. Geological Survey Bulletin 604. Pp. 101, pi. 17, 2 figs. 1915. 



This publication describes the distribution, geology, character, oc- 

 currence, origin, age, and consumption of the Florida phosphates. 

 Several pages are devoted to descriptions of methods of preparing the 

 rock for market. A bibliography of Florida phosphates closes the work. 



There are several different types of phosphate rock in Florida, but 

 only two of them, rock phosphate and land pebble, are important. la 

 the rock phosphate deposits the phosphate is embedded in a fine- 

 grained matrix and a deposit that will yield 25 per cent of valuable 

 rock is regarded as rich. The river pebble deposits are of fluviatile 

 origin and the fragments of which they are composed show mechanical 

 abrasion. The matrix of the river pebble deposits consists of sand and 

 clay. The land pebble is believed to have been derived secondarily 

 from the underlying phosphatic bed rock. 



The deposits are found in sedimentary rocks and with few excep- 

 tions are of secondary origin. They are all of Tertiary age and lie 

 in depressions in the surface of lower Oligocene limestones. The land 

 pebble phosphate has been assigned to the Miocene, but may be as 

 late as Early Pliocene. The river pebble deposits are in part Pleisto- 

 cene and in part Recent. The various theories that have been ad- 

 vanced to explain the origin of the deposits are reviewed at length. 



W. C. Phalen. 



